A Transaction Tax is a tax amount on an order, attributed to a specific authority, with an amount and rate. Other systems call it a Tax Line, Sales Tax, or Tax Detail.

An order can have several tax records to capture several authorities - state plus county plus city, or VAT/GST. This gives accounting and marketplace reconciliation the tax breakdown they need to file and remit correctly. (Line-level tax is also captured on each transaction line; this order-level model is the authority-by-authority breakdown.)